Early tests of an experimental vaccine designed to protect women against a strain of the human papillomavirus that is linked to the development of cervical cancer has shown the vaccine to be 100% effective in preventing infection. "It appears to be the real thing," Christopher Crum, a pathologist at Brigham and Women's Hospital in Boston, told MSNBC.com. "You're looking at some very compelling evidence that this vaccine will prevent cervical cancer."

Virtually all cases of cervical cancer are caused by a handful of strains of HPV. The experimental vaccine targets HPV strain 16, which is linked to about half of all cervical cancer cases. In tests on 1,533 women ages 16 to 23 at 16 sites around the country, the experimental vaccine was shown to prevent HPV-16 infection in all 768 study subjects who received it. Among the 765 women receiving placebo vaccines, 41--or slightly more than 5%--developed persistent HPV infections, and nine women developed precancerous tissue in the cervix. Inoculated women also were shown to have almost 60 times the concentration of virus-fighting antibodies seen in naturally infected women.

A vaccine for cervical cancer is urgently being sought because the disease kills about 225,000 women worldwide each year and is the leading cancer killer of women in developed nations. About 13,000 American women are diagnosed with cervical cancer each year, one third of whom die of the disease.

The full report on the vaccine trial appears in this week's edition of the New England Journal of Medicine.

In an accompanying editorial, Crum writes, "If the promise implicit in the study...is realized, we could in our lifetime see the gradual but progressive dismantling to the barriers to preventing cervical cancer."